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You can try to milk the DI for a good amount, but we've had problems hitting injection window maximums. At some point you either hit the side of the piston as it comes down, or you are fueling while combustion happens--that can cause a misfire. I don't have the paper with all the math on it with me, but at 12-13 psi (70mm pulley) you are going to be awfully close to that limit, especially e85. For that reason a good PI mix is essential. Frankly we've run the tune both at mostly DI, and a mix of DI/PI throughout. End result is that it runs just fine with a DI/PI mix. The knock supression from direct injection does not disappear when you add port injection. We found the same exact thing when tuning NA. In theory DI only should make more power, but the ratios that the car runs (20% PI in stock form) do not really make it any more knock prone. Better just leave it on to clean the valves and keep drivability smooth without all those changeovers. Not relying solely on DI for fueling also gives the ability to time the charge more precisely and make more power.
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